By way of introduction, fluids that are administered intravenously to a patient include blood-based fluids and non-blood fluids, collectively referred to as “intravenous (IV) fluids” herein. While awaiting use, blood-based fluids are maintained in cool storage at approximately 4° C. Non-blood fluids are usually stored at room-temperature.
Moreover, in extreme environmental conditions when the body is exposed to colder temperatures, its internal mechanisms may be unable to replenish the heat that is being lost to the body's surroundings. It is well known that hypothermia poses a significant peril to emergency patients. Intravenous administration of unheated IV fluids, having the extreme environmental temperature, in such patients can cause substantial heat loss and can cause, or at least contribute to, serious patient hypothermia problems and hence aggravate the patient condition.
In the art, it is known to warm IV fluids prior to intravenous administration. However, care must be exercised: overheating IV fluids, especially blood-based compositions, could destroy cells, and endangers the patient life. Examples of method and convection systems for heating IV fluids are disclosed in U.S. Pat. Nos. 4,707,587 and 5,106,373. A heat exchanger may also be employed for keeping the temperature of the IV fluid constant. Unfortunately, this possesses the disadvantage of requiring a large amount of fluid and of increasing the overall size of the apparatus. It is also possible to surround medical tube for carrying and heating the IV fluid with heating elements. It is noted that such heating fluid systems have been described in several patent documents, including U.S. Pat. Nos. 1,995,302; 4,038,519; and 3,355,572 each of which is incorporated by reference in its entirety U.S. Pat. Nos. 1,995,302 and 4,038,519 feature a flexible tube suitable for medical uses in which heating is provided by means of wires or strips of a resistance heating conductor embedded in a helical fashion within the walls of the tubing. U.S. Pat. No. 3,355,572 discloses composite tubing in which heating wires are wound spirally around the inner layer of the tubing and are embedded in the outer layer of the tubing.
While some of the above-mentioned devices are appropriate for their particular uses, they tend to heat in a linear or local manner, resulting in local overheating of the fluid in the conduit. This effect is inconsequential in many applications. A problem arises, however, when heating an IV fluid, such as blood, because it begins to degrade at temperatures of about 45.5° C. Because blood must be heated to regulated normal body temperature (about 37° C.) to achieve optimal results, the conduit must be capable of heating blood uniformly and maintaining its temperature within a narrow range. Another shortcoming of the above-mentioned devices is the inability to accurately monitor the fluid temperature, due to the incapacity of accurately controlling the heat dissipated by heating wires or strips.
Moreover, in order for a bulk warmer to be constantly ready for emergency use, it must be maintained at a proper and set temperature. This requires a system which is bulky, heavy, and/or fixed. The use is impracticable under field emergency conditions, in situations such as military field conditions, pre-hospital such as flight or ambulance conditions or out-patients environment conditions.
U.S. Pat. No. 6,142,974 to Kistner et al. discloses a tube network containing parallel straight sections in the same plane, wrapped in a flexible material which supports resistance heater elements. Unfortunately, in the above-mentioned system fluid leakage often occurs due to the discontinuity of the conduit.
Therefore, there is an ongoing need for a portable safe heating fluid system, stable wider extreme environment conditions transporting and warming any IV fluid infusion at a continuously regulated body temperature, thereby preventing hypothermia.